Date: Tue, 3 Mar 2009 09:22:06 -0600
From: Dimitri Sivanich <sivanich@sgi.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       john stultz <johnstul@us.ibm.com>, linux-kernel@vger.kernel.org
Subject: [PATCH 6/6 v6] SGI RTC: add clocksource driver
Message-ID: <20090303152206.GF20120@sgi.com>
References: <20090303151044.GA20016@sgi.com> <20090303151357.GA20120@sgi.com> <20090303151524.GB20120@sgi.com> <20090303151657.GC20120@sgi.com> <20090303151827.GD20120@sgi.com> <20090303152016.GE20120@sgi.com>
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This patch provides a driver for SGI RTC clocks and timers.

This provides a high resolution clock and timer source using the SGI
system-wide synchronized RTC clock/timer hardware.

Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>

---

Implemented suggested changes and refreshed for latest -tip.

 drivers/clocksource/Makefile |    1 
 drivers/clocksource/rtc_uv.c |  381 +++++++++++++++++++++++++++++++++++++++
 drivers/misc/Kconfig         |    9 
 3 files changed, 391 insertions(+)

Index: linux/drivers/clocksource/Makefile
===================================================================
--- linux.orig/drivers/clocksource/Makefile	2009-03-02 15:02:55.000000000 -0600
+++ linux/drivers/clocksource/Makefile	2009-03-02 15:03:11.000000000 -0600
@@ -2,3 +2,4 @@ obj-$(CONFIG_ATMEL_TCB_CLKSRC)	+= tcb_cl
 obj-$(CONFIG_X86_CYCLONE_TIMER)	+= cyclone.o
 obj-$(CONFIG_X86_PM_TIMER)	+= acpi_pm.o
 obj-$(CONFIG_SCx200HR_TIMER)	+= scx200_hrt.o
+obj-$(CONFIG_SGI_RTC_TIMER)	+= rtc_uv.o
Index: linux/drivers/misc/Kconfig
===================================================================
--- linux.orig/drivers/misc/Kconfig	2009-03-02 15:02:55.000000000 -0600
+++ linux/drivers/misc/Kconfig	2009-03-02 15:03:11.000000000 -0600
@@ -225,6 +225,15 @@ config DELL_LAPTOP
 	This driver adds support for rfkill and backlight control to Dell
 	laptops.
 
+config SGI_RTC_TIMER
+	tristate "SGI RTC driver"
+	depends on GENERIC_CLOCKEVENTS_BUILD
+	depends on X86_UV && SMP
+	default m
+	---help---
+	This option enables RTC event handling and adds the systemwide RTC
+	as a high resolution clock source for SGI systems.
+
 source "drivers/misc/c2port/Kconfig"
 source "drivers/misc/eeprom/Kconfig"
 
Index: linux/drivers/clocksource/rtc_uv.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux/drivers/clocksource/rtc_uv.c	2009-03-02 15:16:17.000000000 -0600
@@ -0,0 +1,381 @@
+/*
+ * SGI RTC clock/timer routines.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ *
+ *  Copyright (c) 2009 Silicon Graphics, Inc.  All Rights Reserved.
+ *  Copyright (c) Dimitri Sivanich
+ */
+#include <linux/module.h>
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <asm/genapic.h>
+#include <asm/uv/uv.h>
+#include <asm/uv/uv_mmrs.h>
+#include <asm/uv/uv_hub.h>
+#include <asm/uv/bios.h>
+
+MODULE_LICENSE("GPL");
+
+#define RTC_NAME		"sgi_rtc"
+
+static cycle_t uv_read_rtc(void);
+static int uv_rtc_next_event(unsigned long, struct clock_event_device *);
+static void uv_rtc_timer_setup(enum clock_event_mode,
+				struct clock_event_device *);
+
+static struct clocksource clocksource_uv = {
+	.name		= RTC_NAME,
+	.rating		= 400,
+	.read		= uv_read_rtc,
+	.mask		= (cycle_t)UVH_RTC_REAL_TIME_CLOCK_MASK,
+	.shift		= 10,
+	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static struct clock_event_device clock_event_device_uv = {
+	.name		= RTC_NAME,
+	.features	= CLOCK_EVT_FEAT_ONESHOT,
+	.shift		= 20,
+	.rating		= 400,
+	.irq		= -1,
+	.set_next_event	= uv_rtc_next_event,
+	.set_mode	= uv_rtc_timer_setup,
+	.event_handler	= NULL,
+};
+
+static DEFINE_PER_CPU(struct clock_event_device, cpu_ced);
+
+/* There is one of these allocated per node */
+struct uv_rtc_timer_head {
+	spinlock_t lock;
+	int next_cpu;	/* next cpu waiting for timer, local node relative */
+	int ncpus;	/* number of cpus on this node */
+	struct {
+		int lcpu;	/* systemwide logical cpu number */
+		u64 expires;	/* next timer expiration for this cpu */
+	} cpu[1];
+};
+
+/*
+ * Access to uv_rtc_timer_head via blade id.
+ */
+static struct uv_rtc_timer_head **blade_info __read_mostly;
+
+/*
+ * Hardware interface routines
+ */
+
+/* Send IPIs to another node */
+static void uv_rtc_send_IPI(int cpu)
+{
+	unsigned long apicid, val;
+	int pnode;
+
+	apicid = per_cpu(x86_cpu_to_apicid, cpu);
+	pnode = uv_apicid_to_pnode(apicid);
+	val = (1UL << UVH_IPI_INT_SEND_SHFT) |
+	      (apicid << UVH_IPI_INT_APIC_ID_SHFT) |
+	      (GENERIC_INTERRUPT_VECTOR << UVH_IPI_INT_VECTOR_SHFT);
+
+	uv_write_global_mmr64(pnode, UVH_IPI_INT, val);
+}
+
+/* Check for an RTC interrupt pending */
+static int uv_intr_pending(int pnode)
+{
+	return uv_read_global_mmr64(pnode, UVH_EVENT_OCCURRED0) &
+		UVH_EVENT_OCCURRED0_RTC1_MASK;
+}
+
+/* Setup interrupt and return non-zero if early expiration occurred. */
+static int uv_setup_intr(int cpu, u64 expires)
+{
+	u64 val;
+	int pnode = uv_cpu_to_pnode(cpu);
+
+	uv_write_global_mmr64(pnode, UVH_RTC1_INT_CONFIG,
+		UVH_RTC1_INT_CONFIG_M_MASK);
+	uv_write_global_mmr64(pnode, UVH_INT_CMPB, -1L);
+
+	uv_write_global_mmr64(pnode, UVH_EVENT_OCCURRED0_ALIAS,
+		UVH_EVENT_OCCURRED0_RTC1_MASK);
+
+	val = (GENERIC_INTERRUPT_VECTOR << UVH_RTC1_INT_CONFIG_VECTOR_SHFT) |
+		((u64)cpu_physical_id(cpu) << UVH_RTC1_INT_CONFIG_APIC_ID_SHFT);
+
+	/* Set configuration */
+	uv_write_global_mmr64(pnode, UVH_RTC1_INT_CONFIG, val);
+	/* Initialize comparator value */
+	uv_write_global_mmr64(pnode, UVH_INT_CMPB, expires);
+
+	return (expires < uv_read_rtc() && !uv_intr_pending(pnode));
+}
+
+/*
+ * Per-cpu timer tracking routines
+ */
+
+static __init void uv_rtc_deallocate_timers(void)
+{
+	int bid;
+
+	for_each_possible_blade(bid) {
+		kfree(blade_info[bid]);
+	}
+	kfree(blade_info);
+}
+
+/* Allocate per-node list of cpu timer expiration times. */
+static __init int uv_rtc_allocate_timers(void)
+{
+	int cpu;
+
+	blade_info = kmalloc(uv_possible_blades * sizeof(void *), GFP_KERNEL);
+	if (!blade_info)
+		return -ENOMEM;
+	memset(blade_info, 0, uv_possible_blades * sizeof(void *));
+
+	for_each_present_cpu(cpu) {
+		int nid = cpu_to_node(cpu);
+		int bid = uv_cpu_to_blade_id(cpu);
+		int bcpu = uv_cpu_hub_info(cpu)->blade_processor_id;
+		struct uv_rtc_timer_head *head = blade_info[bid];
+
+		if (!head) {
+			head = kmalloc_node(sizeof(struct uv_rtc_timer_head) +
+				(uv_blade_nr_possible_cpus(bid) *
+					2 * sizeof(u64)),
+				GFP_KERNEL, nid);
+			if (!head) {
+				uv_rtc_deallocate_timers();
+				return -ENOMEM;
+			}
+			spin_lock_init(&head->lock);
+			head->ncpus = uv_blade_nr_possible_cpus(bid);
+			head->next_cpu = -1;
+			blade_info[bid] = head;
+		}
+
+		head->cpu[bcpu].lcpu = cpu;
+		head->cpu[bcpu].expires = ULLONG_MAX;
+	}
+
+	return 0;
+}
+
+/* Find and set the next expiring timer.  */
+static void uv_rtc_find_next_timer(struct uv_rtc_timer_head *head, int pnode)
+{
+	u64 lowest = ULLONG_MAX;
+	int c, bcpu = -1;
+
+	head->next_cpu = -1;
+	for (c = 0; c < head->ncpus; c++) {
+		u64 exp = head->cpu[c].expires;
+		if (exp < lowest) {
+			bcpu = c;
+			lowest = exp;
+		}
+	}
+	if (bcpu >= 0) {
+		head->next_cpu = bcpu;
+		c = head->cpu[bcpu].lcpu;
+		if (uv_setup_intr(c, lowest))
+			/* If we didn't set it up in time, trigger */
+			uv_rtc_send_IPI(c);
+	} else
+		uv_write_global_mmr64(pnode, UVH_RTC1_INT_CONFIG,
+			UVH_RTC1_INT_CONFIG_M_MASK);
+}
+
+/*
+ * Set expiration time for current cpu.
+ *
+ * Returns 1 if we missed the expiration time.
+ */
+static int uv_rtc_set_timer(int cpu, u64 expires)
+{
+	int pnode = uv_cpu_to_pnode(cpu);
+	int bid = uv_cpu_to_blade_id(cpu);
+	struct uv_rtc_timer_head *head = blade_info[bid];
+	int bcpu = uv_cpu_hub_info(cpu)->blade_processor_id;
+	u64 *t = &head->cpu[bcpu].expires;
+	unsigned long flags;
+	int next_cpu;
+
+	spin_lock_irqsave(&head->lock, flags);
+
+	next_cpu = head->next_cpu;
+	*t = expires;
+	/* Will this one be next to go off? */
+	if (next_cpu < 0 || bcpu == next_cpu ||
+			expires < head->cpu[next_cpu].expires) {
+		head->next_cpu = bcpu;
+		if (uv_setup_intr(cpu, expires)) {
+			*t = ULLONG_MAX;
+			uv_rtc_find_next_timer(head, pnode);
+			spin_unlock_irqrestore(&head->lock, flags);
+			return 1;
+		}
+	}
+
+	spin_unlock_irqrestore(&head->lock, flags);
+	return 0;
+}
+
+/*
+ * Unset expiration time for current cpu.
+ *
+ * Returns 1 if this timer was pending.
+ */
+static int uv_rtc_unset_timer(int cpu)
+{
+	int pnode = uv_cpu_to_pnode(cpu);
+	int bid = uv_cpu_to_blade_id(cpu);
+	struct uv_rtc_timer_head *head = blade_info[bid];
+	int bcpu = uv_cpu_hub_info(cpu)->blade_processor_id;
+	u64 *t = &head->cpu[bcpu].expires;
+	unsigned long flags;
+	int rc = 0;
+
+	spin_lock_irqsave(&head->lock, flags);
+
+	if (head->next_cpu == bcpu && uv_read_rtc() >= *t)
+		rc = 1;
+
+	*t = ULLONG_MAX;
+
+	/* Was the hardware setup for this timer? */
+	if (head->next_cpu == bcpu)
+		uv_rtc_find_next_timer(head, pnode);
+
+	spin_unlock_irqrestore(&head->lock, flags);
+	return rc;
+}
+
+
+/*
+ * Kernel interface routines.
+ */
+
+/*
+ * Read the RTC.
+ */
+static cycle_t uv_read_rtc(void)
+{
+	return (cycle_t)uv_read_local_mmr(UVH_RTC);
+}
+
+/*
+ * Program the next event, relative to now
+ */
+static int uv_rtc_next_event(unsigned long delta,
+			     struct clock_event_device *ced)
+{
+	int ced_cpu = cpumask_first(ced->cpumask);
+
+	return uv_rtc_set_timer(ced_cpu, delta + uv_read_rtc());
+}
+
+/*
+ * Setup the RTC timer in oneshot mode
+ */
+static void uv_rtc_timer_setup(enum clock_event_mode mode,
+			       struct clock_event_device *evt)
+{
+	int ced_cpu = cpumask_first(evt->cpumask);
+
+	switch (mode) {
+	case CLOCK_EVT_MODE_PERIODIC:
+	case CLOCK_EVT_MODE_ONESHOT:
+	case CLOCK_EVT_MODE_RESUME:
+		/* Nothing to do here yet */
+		break;
+	case CLOCK_EVT_MODE_UNUSED:
+	case CLOCK_EVT_MODE_SHUTDOWN:
+		uv_rtc_unset_timer(ced_cpu);
+		break;
+	}
+}
+
+static void uv_rtc_interrupt(void)
+{
+	struct clock_event_device *ced = &__get_cpu_var(cpu_ced);
+	int cpu = smp_processor_id();
+
+	if (!ced || !ced->event_handler)
+		return;
+
+	if (uv_rtc_unset_timer(cpu) != 1)
+		return;
+
+	ced->event_handler(ced);
+}
+
+static __init void uv_rtc_register_clockevents(struct work_struct *dummy)
+{
+	struct clock_event_device *ced = &__get_cpu_var(cpu_ced);
+
+	*ced = clock_event_device_uv;
+	ced->cpumask = cpumask_of(smp_processor_id());
+	clockevents_register_device(ced);
+}
+
+static __init int uv_rtc_setup_clock(void)
+{
+	int rc;
+
+	if (!is_uv_system() ||
+	    register_generic_interrupt_extension(uv_rtc_interrupt, "UVT",
+	    "UV Timer interrupts"))
+		return -ENODEV;
+
+	clocksource_uv.mult = clocksource_hz2mult(sn_rtc_cycles_per_second,
+				clocksource_uv.shift);
+
+	rc = clocksource_register(&clocksource_uv);
+	if (rc) {
+		unregister_generic_interrupt_extension();
+		return rc;
+	}
+
+	/* Setup and register clockevents */
+	rc = uv_rtc_allocate_timers();
+	if (rc) {
+		clocksource_unregister(&clocksource_uv);
+		unregister_generic_interrupt_extension();
+		return rc;
+	}
+
+	clock_event_device_uv.mult = div_sc(sn_rtc_cycles_per_second,
+				NSEC_PER_SEC, clock_event_device_uv.shift);
+
+	clock_event_device_uv.min_delta_ns = NSEC_PER_SEC /
+						sn_rtc_cycles_per_second;
+
+	clock_event_device_uv.max_delta_ns = clocksource_uv.mask *
+				(NSEC_PER_SEC / sn_rtc_cycles_per_second);
+
+	rc = schedule_on_each_cpu(uv_rtc_register_clockevents);
+	if (rc) {
+		clocksource_unregister(&clocksource_uv);
+		unregister_generic_interrupt_extension();
+		uv_rtc_deallocate_timers();
+	}
+
+	return rc;
+}
+module_init(uv_rtc_setup_clock);
--
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